The World Health Organization (WHO) recommends a reference level of 0.1 mSv y⁻¹ for radiological exposure from drinking water, implemented through an adult-based screening framework that does not explicitly account for age-dependent water intake or radionuclide biokinetics. For bone-seeking radionuclides such as Ra-226, these factors can modify both the temporal distribution and cumulative burden of ingestion dose over the lifespan.In this study, an age-dependent lifetime ingestion-dose model was developed for Ra-226 by combining age-specific drinking-water intake rates with International Commission on Radiological Protection (ICRP) ingestion dose coefficients and time-resolved biokinetic dose functions. Annual and cumulative effective doses were calculated from birth to 70 years and compared with estimates obtained using the adult-only screening approach, assuming a constant drinking-water concentration of 1 Bq L⁻¹.The cumulative lifetime effective dose reached approximately 0.020 Sv, corresponding to a lifetime-averaged annual dose of ~0.29 mSv y⁻¹, compared with ~0.20 mSv y⁻¹ derived using the adult-based method. Although the absolute magnitude of Ra-226 ingestion dose is lower than that reported for Ra-228, the age-dependent model revealed a clear early-life dominance.The highest annual dose occurred during the first year of life (~1.2 mSv y⁻¹), driven by elevated infant ingestion dose coefficients. Annual dose declined rapidly through early childhood and then approached a near-constant adult value of approximately 0.2 mSv y⁻¹.In contrast to Ra-228, Ra-226 did not produce a pronounced adolescent dose peak, reflecting faster dose saturation following intake and limited long-term contribution from short-lived progeny. These results demonstrate that adult-only screening does not capture the timing and distribution of Ra-226 ingestion dose and that age-dependent lifetime modeling provides a more realistic basis for assessing chronic exposure from drinking water.
Alnajjar et al. (Mon,) studied this question.